In my time at Leyland, Series III 88" had 6.00 x 16 cross ply, usually military bar tread, and 109" had 7.50 x 16 cross ply, mbt's or dual purpose tyres, mostly Dunlop or Olympic. Forget what the dual purpose ones were called. Some 88" were retro-fitted with 7.50's before sale at dealer/customer request. For Qld. we preferred Olympic as state and local govt. vehicles were supposed to be delivered on Qld. made tyres and Olympics were the only brand to have a plant in Qld, now closed. Other customer requests were usually a preference for a particular brand, or for Goodyear Custom Hi-milers for beach work, or, rarely, Michelin Sahara. The Michelins were luxury priced.